Wednesday, December 29, 2004

ATOMS are the fundamental building blocks of matter, which means they are very small indeed. The world at the scale of atoms and molecules is difficult to describe and hard to imagine. It is so odd that it even has its own special branch of physics, called quantum mechanics, to explain the strange things that happen there. If you were to throw a tennis ball against a brick wall, you might be surprised if the ball passed cleanly through the wall and sailed out on the other side. Yet this is the kind of thing that happens at the quantum scale. At very small scales, the properties of a material, such as colour, magnetism and the ability to conduct electricity, also change in unexpected ways.

It is not possible to “see” the atomic world in the normal sense of the word, because its features are smaller than the wavelength of visible light. But back in 1981, researchers at IBM designed a probe called the scanning tunnelling microscope (STM), named after a quantum-mechanical effect it employs. Rather like the stylus on an old-fashioned record player, it could trace the bumps and grooves of the nanoscale world. This allowed scientists to “see” atoms and molecules for the first time. It revealed landscapes as beautiful and complex as the ridges, troughs and valleys of a Peruvian mountainside, but at the almost unimaginably small nanometre (nm) scale.

A nanometre is a billionth of a metre, or roughly the length of ten hydrogen atoms. Although scientists had thought about tinkering with things this small as long ago as the late 1950s, they had to wait until the invention of the STM to make it possible. More here